1. Field of the Invention
The present invention relates to an electric signal taking-out method and a device therefor, which are used for taking out an electric signal or signals for measurement from an arbitrary place of a circuit board mounted to electronic/electric equipment when the equipment is checked, adjusted or repaired.
2. Description of the Related Art
A small electronic part which is mounted on a printed circuit board and is referred to as a chip part, such as a resistor, capacitor or the like, is formed to have an extremely small rectangular parallelepiped configuration which has a length of 0.3 to 1.25 mm, a width of 0.2 to 0.6 mm and a height of 0.25 to 0.6 mm. A circuit board is constructed so that such chip parts are mounted onto a circuit pattern formed on a front surface and/or a back surface of the circuit board by soldering. When a chip part is soldered to the surface of the circuit board, solder rises from the surface of the circuit board to an upper surface edge of the chip part in such a manner as to form an inclined surface on the solder affixed to each of opposite end surfaces of the chip part.
In the case where a signal line on the circuit board during development or on the circuit board completed as a product is checked, it is necessary to take out an electric signal or signals for measurement from the solder joints of the chip parts and feed it/them to a measuring apparatus. Conventionally, in order to take out an electric signal or signals for measurement from the circuit board which has chip parts soldered thereto as mentioned above, tweezers having two arms insulated from each other are held by a user""s fingers, and the two arms are pressed so that distal end electrodes thereof are pressedly brought into contact with the solder joints at the opposite ends of the chip part. In this state, while the tweezers are being held, an electric signal or signals is/are taken out so as to be checked by the measuring apparatus.
In another conventional technique, metal pieces or chips with a hole, which are adapted to be clamped or caught by a commonly used clip, probe or the like, are previously soldered to side surfaces of an electronic part, and ends of the metal chips rising from an upper surface of the circuit board are clamped by the clip, probe or the like, as desired, whereby an electric signal or signals is/are taken out so as to be output to the measuring apparatus. Such a metal chip is formed to have approximately the same size as that of the electronic part, and the metal chip as well as the chip part are soldered to the circuit board while the metal chip is kept in contact with the end of the chip part.
In the former conventional technique of bringing the end electrodes into contact with the chip part, when the user""s hand is taken off the tweezers, the electrodes are disengaged from the electronic part, and thus pressing of the tweezers should be continued during the measurement. For this reason, in the case of measurement requiring a long time, there arises a problem that work efficiency is very low. Moreover, even if both hands are used, electric signals in only two places can be taken out, that is, electric signals cannot be taken out arbitrarily from many places. Therefore, an analysis of multi-signals simultaneously taken out cannot be made by using an electronic measuring apparatus of a multi-signal simultaneous analysis type, such as a logic analyzer or the like.
Further, in the latter conventional technique of soldering the metal chip for a clip to the side surface of the electronic part, the material cost and the man-hour cost rise. Moreover, although a number of such electronic parts referred to as chip parts are used in a variety of recent small electronic equipment, metal chips for measurement cannot be mounted to all the mounted chip parts, and thus electric signals cannot be taken out from arbitrary places. Moreover, since a chip part has been further miniaturized and chip density on a circuit board has become high recently, it is difficult to provide a space for mounting metal chips for measurement on the circuit board, so that arrangement of metal chips for measurement cannot be effected.
The present invention has been made in order to solve the above mentioned problems of the conventional techniques. Accordingly, an object of the present invention is to provide an electric signal taking-out method and a device therefor which are capable of easily taking out an electric signal or signals for measurement from opposite ends of an arbitrary chip part soldered to a circuit board without a user""s hand having to hold tweezers during measurement or without previously soldering metal chips or the like for measurement to an electronic part.
According to one aspect of the present invention, an electric signal taking-out method is provided. The method includes the steps of: arranging a pair of contact elements which include sharp distal ends and are bent obliquely inward so as to be opposite to each other so that the sharp distal ends face each other; shifting the pair of contact elements inward so as to make the sharp distal ends thereof bite into solder joints by which a chip part is soldered to a circuit board; and holding the pair of contact elements in a biting state, to thereby take out electric signals independently from the pair of contact elements.
According to another aspect of the present invention, an electric signal taking-out device is provided. The device includes: a pair of contact elements made of an electrically conductive material, each including a distal end portion which is bent obliquely inward and which has a sharp distal end, the pair of contact elements being arranged in such a manner as to be electrically insulated from each other and to be opposite each other while the sharp distal ends thereof face each other; and a holding member for drawing the pair of contact elements toward each other so as to press the distal ends of the contact elements onto an object to be measured, to thereby make the distal ends of the contact elements bite into the object, and holding the pair of contact elements in a state where the distal ends of the pair of contact elements are biting into the object.
In a preferred embodiment of the present invention, the device further includes a supporting member having the pair of contact elements mounted thereto and provided with a guide section; wherein the holding member is slidably fitted on the guide section of the supporting member so as to be moved between a first position and a second position, whereby when the holding member is located in the first position, a spacing between the distal ends of the pair of contact elements becomes large, and when the holding member is located in the second position, the spacing between the distal ends of the pair of contact elements becomes small.
In a preferred embodiment of the present invention, the holding member is provided with a brake piece which is elastically engaged with the guide section of the supporting member so as to keep the holding member stopped at an arbitrary position with respect to the supporting member.
In a preferred embodiment of the present invention, the holding member has electric conductors led out to the outside and is provided on a distal end thereof with a pair of fixed pins which are formed of an electrically conductive material and which come in contact with outside surfaces of the pair of contact elements so as to shift the pair of contact elements inward, the fixed pins being connected with the electric conductors, respectively.
In a preferred embodiment of the present invention, the device further includes a spring, disposed between the supporting member and the holding member, for biasing the holding member toward the second position.
In a preferred embodiment of the present invention, the pair of contact elements include proximal portions which are formed integrally with the supporting member, and the supporting member has electrically conductive leads led out to the outside and connected with ends of the proximal portions of the contact elements, respectively.
In a preferred embodiment of the present invention, the supporting member includes an isolation piece extending between the pair of contact elements toward the distal ends of the contact elements so as to prevent the pair of contact elements from coming into contact with each other.